This invention relates to a color-stabilized dentifrice composition comprising a cinnamic aldehyde or citral flavorant which is subject to discoloration/yellowing upon aging, and a trisubstituted double bond-containing terpene or sesquiterpene which significantly reduces and/or prevents discoloration, and maintaining the pH of said composition below 8.5 and preferably at a neutral to acid pH. The dentifrice must be free of oxidizing agents such as hydrogen peroxide, or salts delivering hydrogen peroxide such as sodium perborate, peracids and salts of peracids.
The prior art is replete with dental formulations comprising the combination of a cinnamic aldehyde or citral flavorant and a terpene as shown in U.S. Pat. Nos. 3,867,557 and 3,928,560 wherein oral compositions containing 0.0001-20% paramethoxycinnamaldehyde flavoring agent is dissolved in 100 parts orange oil (Example VII), and 4% of the cinnamaldehyde is dissolved in 500 ml ethyl alcohol and 10 ml orange oil (Example XIII). Essential oils such as orange oil are known to contain terpenes. U.S. Pat. No. 4,001,438 also discloses flavor formulations containing citral and orange terpenes (Example B in column 10) to be used in oral compositions. However, there is no recognition in this group of patent of the discoloration or yellowing problem associated with the use of the cinnamic aldehyde flavorant. These patents relate to different aspects in dentifrice formulations. The disclosure of the combination of cinnamic aldehyde flavorant and a terpene is incidental to a general discussion of flavorants.
The prior art also recognizes the fading and/or deterioration of flavors or dyes as shown in U.S. Pat. No. 3,666,496 wherein a poly(oxyethylene)-poly(oxypropylene)copolymer is added to terpene containing flavors such as orange oil to prevent deterioration of the flavor to be used in flavored foods or beverages. U.S. Pat. No. 4,305,928 adds 0.05-5% phytic acid and/or benzoic acid as a chelator to prevent or reduce color fading of red or yellow monazo or blue triarylmethylene dye-colored visually clear dentifrice. U.S. Pat. No. 3,957,964 discloses a dentifrice containing encapsulated flavoring which provides a more stable and fresher tasting flavored dentifrice. However, there is no mention in aforesaid patents of the stabilization of the cinnamic aldehyde or citral flavor with a specific group of terpenes or sesquiterpenes characterized by a trisubstituted double bond.
U.S. Pat. No. 2,184,526 also recognizes the instability against oxidation by air of p-isopropyl-.alpha.-methylhydrocinnamic aldehyde as a perfume ingredient, wherein the aldehyde is converted into the corresponding acid, thereby destroying the aldehyde odor. The addition of alcohols of the aromatic or terpene series stabilizes the aldehyde against air oxidation, by converting the aldehyde into a hemi-acetal of said alcohol.
U.S. Pat. No. 3,671,630 discloses the use of multiple classes of terpenes as color stabilizers for aqueous halogenated phenolic germicidal compositions which discolor within a few hours of exposure to light. However, many terpenes such as limonene have been disclosed to be ineffective. The halogenated phenolic germicidal compounds cannot be equated to the cinnamic aldehyde or citral flavorants which are unsaturated aldehydes. In addition, it is noted that limonene, one of the terpenes specifically used as a color stabilizer for the flavorant, is specifically excluded as ineffective in stabilizing the germicidal composition.
None of the above cited art discloses the use of a specific group of terpenes or sesquiterpenes in a dentifrice, free of oxidizing agents and maintained at an acid or neutral pH, containing the cinnamic aldehyde or citral flavor, to reduce discoloration of said flavorant upon aging.